1. Field of the Invention
The present invention relates generally to a pressure-retaining disk for use in an apparatus to penetrate into a pressure vessel for purposes of introducing sensors.
2. Description of Prior Art
Thermocouples are typically used to measure temperature within reactors or other vessels. The introduction of the thermocouples or other sensor devices into the vessel requires an assembly that is attached or coupled to the vessel such that the sensors are encapsulated within a sensor assembly that allows the sensors to penetrate into the interior of the vessel. The sensors exit the vessel or the sensor well to an instrumentation junction box containing electrical terminals for transmitting the temperature signal of the thermocouples or signal related to any other property to be measured by the sensor. Commonly, multiple thermocouples are used to allow for placement at different locations within the vessel. The term sensor is used throughout in its broadest sense to indicate thermocouples and other sensing devices. Specific references to thermocouples are understood to apply to other sensing devices as well.
For operational as well as safety reasons, it is necessary to create a pressure seal to prevent pressure escape in the area where the sensor leads exit the vessel and enter the instrument junction box. For example, it is necessary to create a high pressure primary seal so that fluid or gas from the vessel does not escape. The secondary seal acts to give a second layer of defense should a problem occur and it provides a warning of primary seal loss. Multi-holed plates or disks, such as the thermocouple seal disclosed in U.S. Pat. No. 4,376,227 issued to Hilborn, are used for this purpose. Sensors are passed through the holes of the disk and brazed or welded to the shields extending through the disk.
U.S. Pat. No. 5,232,517 also issued to Hilborn discloses a multipoint sensor assembly for measuring temperature at a large number of discrete locations within a vessel. Multiple sensors enter the vessel through a pressure-retaining multi-holed disk.
U.S. Pat. No. 5,775,807 issued to Dutcher discloses an apparatus for maximizing multi-tubular penetration of a pressure vessel allowing the introduction of multiple sensors. The sensor cables are secured to multi-holed pressure-retainer disks. The apparatus includes a first pressure-retaining disk that forms a primary chamber between the disk and the flange which provides a separation area for the temperature measurement cables. A second pressure-retaining disk creates a secondary chamber between the first and second pressure-retaining disks. The second pressure-retaining disk closes the other end of the tubular sensor apparatus. The temperature measurement cables extend at one end into the pressure vessel and at the other end through aligned holes in the disks and to instrumentation. Each sensor is welded to one face of each disk. Pressure taps can be utilized attached to the first and/or second chamber. An option pressure tap into the primary chamber allows the operator to determine the pressure of the vessel since it is always under pressure while the vessel is operation. Another means of gathering this pressure reading is through an additional opening in the vessel, additional openings being undesirable.
While the thermocouple seal described above and the apparatus described in the ""807 patent has been quite successful, it is desirable to create a sensor assembly that maximizes pressure retention while minimizing the space required for the apparatus. Thus, it is an object of the invention to create a pressure disk that allows for a minimization of size and weight of a sensor assembly. Likewise, it is an object to lower material costs of a sensor assembly. It is a further object of the invention to maximize the allowable pressure rating for a sensor assembly.
It is a further object of the invention to create a disk that not only permits the passage of temperature measurement devices but also permits the monitoring of pressure.
It is an object of the invention to create a pressure-retaining disk that not only creates a seal to make a primary pressure chamber, but also acts as a self-contained secondary pressure chamber.
It is an object of the invention to create a pressure-retaining disk that allows the venting of pressure build-up.
It is an object of the invention to reduce the number of weld splices required, as compared to previous assembly designs, to reduce the number of potential leak points.
It is an object of the invention to lower inspection and pressure testing costs. It is a further object of the invention to lower manufacturing costs.
It is an object of the invention to minimize the possibility of assembly error such as misalignment of pass-through bores in a multi-disk chamber design.
It is an object of the invention to provide a pressure tap connection integral to the pressure-retaining disk.
The current invention, which addresses one or more of the above objects, includes a sealing device which includes a pressure-retaining disk for use with a sensor assembly. The pressure-retaining disk receives a plurality of sensor leads, the disk having a plurality of sensor-receiving bores for receiving the sensor leads. These bores are connected by a passage. The passage between the bores creates a network where the pressure in the bores and the passage are equalized. Thus, a pressure reading at any point in the network, whether it is a bore or a passage, is effectively the same.
The pressure-retaining disk has an inner surface that is exposed to the pressure of the vessel. The disk also has an outer surface which is the rest of the surface area, such area being unexposed to the pressure of the vessel. A preferred embodiment includes an aperture in the disk between the network and the outer surface of the pressure-retaining disk. In this manner, a pressure-measuring device can be used in conjunction with the aperture to monitor the pressure. This aperture thus allows for the indication of a loss of a primary seal or of hydrogen migration. The aperture can also be used as a means for venting pressure build-up.
In one embodiment of the invention, the passage is non-perpendicular to the bores which the passage connects thus creating an angled connection.
The pressure-retaining disk includes tube means fixed to the disk generally aligning with at least a plurality of the sensor-receiving bores. The tubes or other tube means receive the sensors which pass through the bores. While the tubes can also include openings that align with the bores, a preferred embodiment includes attaching the tubes to the surfaces of the disk such that the tube extends from a first face of the disk with a corresponding tube extending from a second face of the disk in alignment with the same bore. When the tube means is a sheath for the sensor, it is the tube means that is connected to the disk and the sheath can extend all the way into the reactor. In such situation, the sheath passes through though the bore without an opening in the sheath aligning with passage as the invention allows monitoring of the equalized pressure in the bores through which the sheaths pass.
The pressure-retaining disk is part of an apparatus that sealingly closes an entry to a pressure vessel where the pressure vessel includes a sensor assembly for passing a plurality of sensors at least partially into the vessel through an opening in the vessel. Again, tubes can be fixed to the disk through the bores for receiving the sensors when desired. The apparatus includes means for mounting the pressure-retaining disk to the vessel at the opening in the vessel. In one embodiment, the pressure-retaining disk described above connects directly to the mounting means. The mounting means can be any traditional or non-traditional sealing method. Examples include a flange, such as a standard flange including a circle of bolt holes compatible with a like circle of holes carried by a nozzle of the vessel, the nozzle providing the opening in the vessel. The flange may include a tubular bore through the flange or individual bores for receiving the sensors or other configurations. An example of a non-traditional sealing method includes a proprietary fitting attached to the vessel.
Another embodiment of the mounting means useful in the apparatus includes a tubular body with an opening through it and fastener means. In this situation, fastener means includes any type of sealing method as described above with the tubular body attached thereto. The sensors pass through the bore in the pressure-retaining disk into and through the tubular body. The sensors are introduced into the vessel through the opening of the tubular body and the fastener means. The tubular body has a first end located adjacent to the fastener means or, with some proprietary fasteners, within the vessel. A second end of the tubular body is connected to the pressure-retaining disk such that pressure of the vessel is retained within the tubular body. When this configuration is used, the tubular body is at least partially located between the disk and the fastener means. The tubular body can be of cylindrical shape or of some other shape such that the opening in the tubular body creates a channel through which the sensors can pass. A common configuration includes a tubular body that changes diameters along its length or xe2x80x9cnecks down.xe2x80x9d